/**
*      author: Y_Yao
*      created: 2025-03-01 12:36:05
**/

#include<bits/stdc++.h>

#define int LL
using namespace std;
using LL = long long;
const LL LLINF = 1e18;
const int INF = 0x3f3f3f3f;
string s,t;
int n;

void solve()
{
    cin >> n;
    cin >> s;
    cin >> t;
    int cnt = 0;
    for(int i = 1;i <= n;i++)
    {
        if(s.substr(n - i) == t.substr(0,i))
        {
            cnt = i;
        }
    }
    int ans = s.size() - cnt + t.size() - cnt + cnt;
    cout << ans << endl; 
}

signed main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);

    int t = 1;
    //cin >> t;
    while(t--)
    {
        solve();
    }
    return 0;
}